looked the more he was impelled to investigate. Finally curiosity
prevailed.

The door of the cab was closed and he looked inside.

The cab was empty.

As he opened the door, the sleeping horse came suddenly to life; with a
snort it struggled to its feet, then looked around apologetically at
Harleston, as though begging to be excused for having been caught in a
most reprehensible act for a cab horse.

"That's all right, old boy," Harleston smiled. "You doubtless are in
need of all the sleep you can get. Now, if you'll be good enough to
stand still, we'll have a look at the interior of your appendix."

The light from the street lamps penetrated but faintly inside the cab,
so Harleston, being averse to lighting a match save for an instant at
the end of the search, was forced to grope in semi-darkness.

On the cushion of the seat was a light lap spread, part of the equipment
of the cab. The pockets on the doors yielded nothing. He turned up the
cushion and felt under it: nothing. On the floor, however, was a woman's
handkerchief, filmy and small, and without the least odour clinging to
it.

"Strange!" Harleston muttered. "They are always covered with perfume."

Moreover, while a very expensive handkerchief, it was without
initial--which also was most unusual.